The Lib Non-Dems have joint acting leaders at the moment, Sir Ed Davey and somebody called Mark Pack. Ed Davey is also the Deputy Leader and Mark Pack the President (I think they have to multi-task due to a lack of staff).
Jo Swinson stepped down as leader immediately upon losing her Parliamentary seat at the General Election. For those who cannot remember, Ms Swinson was the one time - for about a fortnight - self-styled "next Prime Minister". The Lib Non-Dems rules say that their leader must be a Westminster MP - something that may present them with a problem in the future.